The invention relates to a protective material with punched shaped parts obtainable in a converting process for producing single-sidedly or double-sidedly adhesive punched shaped parts, there being placed atop the protective material a single-sidedly or double-sidedly adhesive tape from which punched shaped parts are punched out by means of punching tools, in particular by the kiss-cut process, and also to the use of a polymer backing for a protective material of this kind.
Parts which are to be fastened by means of double-sided adhesive tape (for example, electronic components or seals in mobile telephones) require the use, depending on the particular application, of double-sidedly adhesively punched parts. These punched parts have to be converted into the required form beforehand in a punching process, particularly by the process known as kiss cutting, which in turn requires the adhesive tape that is present for producing the punched parts to be protected beforehand with a material having antiadhesive properties. To produce punched parts which are composed of the adhesive tape individually or, by lamination, of a composite with particularly hard, inflexible materials such as, for example, polyester, it is preferred to use a likewise hard, inflexible backing sheet as the protection. This removes the possibility of the backing sheet yielding under the developing pressure of the punching dies during penetration of hard punched shaped parts, and the punching dies penetrating too greatly into the backing sheet.
A feature of the kiss-cut process is that, during punching, the material which has antiadhesive properties is injured or punched very little if at all.
For the dispensing procedure of the punched shaped parts, it is common—depending on the guiding process—to use transparent or opaque polyester films as the hard backing sheet. When opaque polyester backing sheets are used, guiding can be carried out by means of optical recognition systems such as, for example, light barrier advance systems in conjunction with holelike notches in the edge region of the backing sheet.
The opacity of the polyester film is normally brought about by homogeneous incorporation of pigmentary fillers such as, for example, carbon black or titanium dioxide into the polyester. In general, depending on the recognition method of the punched shaped parts on the backing sheet in the guiding process, transparent white- or black-colored polyester backing sheets are employed, the backing sheet filled with the white pigment titanium dioxide having the disadvantage that the punching dies are subject to severe abrasion, leading to more frequent and costly reworking and changing of the punching die. On the other hand, black-colored polyester backings may, because of the carbon black fraction, alter the electrical conductivity properties of the backing web and cause faults in the recognition systems.
It is an object of the invention to provide an opaque polymer backing sheet, suitable for web edge guided optical recognition systems, for converting and dispensing adhesive punched shaped parts, which owing to the nature of its coloring prevents abrasion of the punching dies or changes in the electrical conductivity of the backing sheet.